Soxi warn about missing extended part of the fmt chunk--but it seems to be there

Sylvain Leroux <[email protected]> Fri, 22 Nov 2019 16:10:21 +0100
Newsgroups	gmane.comp.audio.sox
Message-ID	<[email protected]>
Hi everyone.

First thank you for the great work and support. I'm in the process of
writing a sound library for an internal project, and I realize more each
day the amount of work the developers may have put in writing SoX.

I am working now on a Wave file exporter, and while using `soxi` to
verify the my wave files are well formed, I noticed the warning "wave
header missing extended part of fmt chunk":


> sh$ soxi -V4 test/tmp/float_32_1.wav
> soxi INFO formats: detected file format type `wav'
> soxi DBUG wav: WAV Chunk fmt
> soxi INFO wav: EXTENSIBLE
> soxi WARN wav: wave header missing extended part of fmt chunk
> soxi DBUG wav: WAV Chunk fact
> soxi DBUG wav: WAV Chunk data
> soxi DBUG wav: Reading Wave file: IEEE Float format, 1 channel, 48000
> samp/sec
> soxi DBUG wav:         192000 byte/sec, 4 block align, 32 bits/samp,
> 643200 data bytes
> soxi DBUG wav:         160800 Samps/chans
>
> Input File     : 'test/tmp/float_32_1.wav'
> Channels       : 1
> Sample Rate    : 48000
> Precision      : 24-bit
> Duration       : 00:00:03.35 = 160800 samples ~ 251.25 CDDA sectors
> File Size      : 643k
> Bit Rate       : 1.54M
> Sample Encoding: 32-bit Floating Point PCM

However, it seems to me I write the extended 40 bytes fmt chunk in the file:

> 00000000  52 49 46 46 cc d0 09 00  57 41 56 45 66 6d 74 20  |RIFF....WAVEfmt |
> 00000010  28 00 00 00 fe ff 01 00  80 bb 00 00 00 ee 02 00  |(...............|
> 00000020  04 00 20 00[16 00]20 00  00 00 00 00 03 00 00 00  |.. ... .........|
> 00000030  00 00 10 00 80 00 00 aa  00 38 9b 71 66 61 63 74  |.........8.qfact|
> 00000040  04 00 00 00 80 d0 09 00  64 61 74 61 80 d0 09 00  |........data....|
> 00000050  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
> *
> 0009d0d0

At byte 0x24 we can see 0x0016 which is the size (22 bytes) of the
extended fmt header, followed by the extended header content. And after
that, the `fact` chunk starts.

Why is `soxi` considering the extended header is missing?

FWIW, Microsoft docs seem to be relatively ambiguous, so
I based my wave exporter implementation on
http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/WAVE/WAVE.html

I don't know if I can attach files to this mailing list, but let me know
if you want I send you the corresponding Wave file.

Best regards,
- Sylvain Leroux

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